Network Security

Network Security

Objectives • Types of Attacks • Attacks on the OSI & TCP/IP Model • Attack Methods • Prevention • Switch Vulnerabilities and Hacking • Cisco Routers • Interesting links

Physical Access Attacks Wiretapping Server Hacking Vandalism Dialog Attacks Eavesdropping Impersonation Message Alteration Types of Attacks

Social Engineering Opening Attachments Password Theft Information Theft Penetration Attacks Scanning (Probing) Break-in Denial of Service Malware Viruses Worms Types of Attacks (Cont.)

Risk Analysis of the Attack • What is the cost if the attack succeeds? • What is the probability of occurrence? • What is the severity of the threat? • What is the countermeasure cost? • What is the value to protect the system • Determine if the countermeasure should be implemented. • Finally determine its priority.

OSI & TCP/IP Related Attacks

Session Password theft Unauthorized Access with Root permission Transport & Network: Forged TCP/IP addresses DoS Attacks Application layer: Attacks on web Attacks are typically virus Presentation: Cracking of encrypted transmissions by short encryption key OSI Model Related Attacks

Data Link & Physical Network Sniffers Wire Taps Trojan Horses Malicious code OSI Model Related Attacks

Attacks Related to TCP Packet • Port Number • Applications are identified by their Port numbers • Well-known ports (0-1023) • HTTP=80, Telnet=23, FTP=21 for supervision, 20 for data transfer, SMTP=25 • Allows applications to be accessed by the root user

Attacks Related to TCP Packet • IP address spoofing • Change the source IP address • To conceal identity of the attacker • To have the victim think the packet comes from a trusted host • LAND attack

Attacks Related to TCP Packet • Port Number • Registered ports (1024-49152) for any application • Not all operating systems uses these port ranges, although all use well-known ports

Attack Methods

Attack Methods • Host Scanning • Network Scanning • Port Scanning • Fingerprinting

Attack Methods (Cont.) • Host Scanning • Ping range of IP addresses or use alternative scanning messages • Identifies victims • Types of Host scanning • Ping Scanning • TCP SYN/ACK attacks

Attack Methods (Cont.) • Network Scanning • Discovery of the network infrastructure (switches, routers, subnets, etc.) • Tracert and applications similar identifies all routers along the route to a destination host

Attack Methods (Cont.) • Port Scanning • Once a host is identified, scan all ports to find out if it is a server and what type it is • Two types: • Server Port Scanning • TCP • UDP • Client Port Scanning • NetBIOS • Ports 135 – 139 used for NetBIOS ports used for file and print services. • GRC.com a free website that scan your pc for open ports.

Attack Methods (Cont.) • Fingerprinting • Discovers the host operating system and applications as well as the version • Active (sends) • Passive (listen) • Nmap does all major scanning methods

Attack Methods (Cont.) • Denial-of-Service (DoS) Attacks • Attacks on availability • SYN flooding attacks overload a host or network with connection attempts • Stopping DoS attacks is very hard.

Attack Methods (Cont.) • The Break-In • Password guessing • Take advantage of unpatched vulnerabilities • Session hijacking

After the Compromise • Download rootkit via TFTP • Delete audit log files • Create backdoor account or Trojan backdoor programs

After the Compromise (Cont.) • Weaken security • Access to steal information, do damage • Install malicious software (RAT, DoS zombie, spam relay, etc.)

Prevention

Stealth Scanning Access Control Firewalls Proxy Servers IPsec Security Policies DMZ Host Security Preventions

Stealth Scanning • Noisiness of Attacks • Exposure of the Attacker’s IP Address • Reduce the rate of Attack below the IDS Threshold • Scan Selective Ports

Access Control • The goal of access control is to prevent attackers from gaining access, and stops them if they do. • The best way to accomplish this is by: • Determine who needs access to the resources located on the server. • Decide the access permissions for each resource. • Implement specific access control policies for each resource. • Record mission critical resources. • Harden the server against attacks. • Disable invalid accounts and establish policies

Firewalls are designed to protect you from outside attempts to access your computer, either for the purpose of eavesdropping on your activities, stealing data, sabotage, or using your machine as a means to launch an attack on a third party. Firewalls

Hardware Provides a strong degree of protection from the outside world. Can be effective with little or no setup Can protect multiple systems Software Better suite to protect against Trojans and worms. Allows you to configure the ports you wish to monitor. It gives you more fine control. Protects a single system. Firewalls (Cont.)

Firewalls • Can Prevent • Discovery • Network • Traceroute • Penetration • Synflood • Garbage • UDP Ping • TCP Ping • Ping of Death

Proxy • A proxy server is a buffer between your network and the outside world. • Use an anonymous Proxy to prevent attacks.

IPSec • Provides various security services for traffic at the IP layer • These security services include • Authentication • Integrity • Confidentiality

IPsec overview - how IPsec helps

DMZ Image

Host Security • Hardening Servers • Cisco IOS • Upgrades and Patches • Unnecessary Services • Network Monitoring tools

Switch Vulnerabilities and Hacking

CDP Protocol • Used to locate IP address, version, and model. • Mass amounts of packets being sent can fake a crash • Used to troubleshoot network, but should be disabled.

ARP Poisoning • Give users data by poisoning ARP cache of end node. • MAC address used to determine destination. Device driver does not check. • User can forge ARP datagram for man in the middle attack.

SNMP • SNMP manages the network. • Authentication is weak. Public and Private community keys are clear text. • Uses UDP protocol which is prone to spoofing. • Enable SNMPv3 without backwards compatibility.

Spanning Tree Attacks • Standard STP takes 30-45 seconds to deal with a failure or Root bridge change. • Purpose: Spanning Tree Attack reviews the traffic on the backbone.

Spanning Tree Attacks • Only devices affected by the failure notice the change • The attacker can create DoS condition on the network by sending BPDUs from the attacker.

Spanning Tree Attacks (Cont.) • STEP 1: MAC flood the access switch • STEP 2: Advertise as a priority zero bridge.

Spanning Tree Attacks (Cont.) Spanning Tree Attacks (Cont.) • STEP 3: The attacker becomes the Root bridge! • Spanning Tree recalculates. • The backbone from the original network is now the backbone from the attacking host to the other switches on the network.

STP Attack Prevention • Disabling STP can introduce another attack. • BPDU Guard • Disables ports using portfast upon detection of a BPDU message on the port. • Enabled on any ports running portfast

STP Attack Prevention • Root Guard • Prevents any ports that can become the root bridge due to their BPDU

CSM and CSM-S • Cisco Content Switching Modules • Cisco Content Switching Module with SSL

CDM • Cisco Secure Desktop • 3 major vulnerabilities • Maintains information after an Internet browsing session. This occurs after an SSL VPN session ends. • Evades the system via the system policies preventing logoff, this will allow a VPN connection to be activated. • Allow local users to elevate their privileges.

Prevention • Cisco has software to address the vulnerabilities. • There are workarounds available to mitigate the effects of some of these vulnerabilities.

Cisco Routers

Cisco Routers • Two potential issues with Cisco Routers • Problems with certain IOS software • SNMP

Devices running Cisco IOS versions 12.0S, 12.2, 12.3 or 12.4 • Problem with the software • Confidential information can be leaked out • Software updates on the CISCO site can fix this problem

Virtual Private Networks Virtual connection 1 Virtual Connection 2

Network Security